JPH09174604A - Torpedo for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torpedo for injection molding which has a shape enabling molding of a cathide alloy by an injection molding method. SOLUTION: A torpedo has a tip 74 having a pointed fore end and a conical front 72 forming a molten material passage 64 extending to an outlet 80. The molten material passage 64 has the rear area 92 extending from an inlet 78 on the rear side 70 of the torpedo and a slant front area 94 extending from the rear area 92 to the outlet 80. This front area 94 is given an angle being enough to make it possible to push out the molded torpedo freely from a mold, while a taper is kept inside. For this, the taper needs to be sufficient for that the shortest longitudinal line 116 along the inner surface 114 forming the molten material passage 64 is not off outward anywhere along the direction of the length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus, and more particularly to an injection molding torpedo manufactured by molding a carbide alloy that is mounted concentrically with a gate and is mounted on the front end of a nozzle.

[0002]

2. Description of the Related Art
Chip torpedo with a melted material passageway with an oblique front section extending to a conical front-facing outlet, as shown in the Moldmaster, Inc. brochure entitled "DURA Hot Runner System" dated September 1995. Is already known. However, the molten material passages in these conventional torpedo are not formed in a tapered shape, but are produced by plating a copper alloy or by machining a high thermal conductive material. While these torpedes are satisfactory for some applications, these materials are not sufficient to withstand the corrosion and wear experienced by molten material through the torpedo.

On the other hand, it is known that a carbide alloy has excellent corrosion resistance and wear resistance as compared with these materials. However, it is extremely difficult to machine a carbide alloy, and it is too costly to machine these conventional torpedoes made of a carbide alloy.

In order to manufacture a metal product, a method is known in which a metal powder melted in a metal injection molding process is molded, further depolymerized, and heated and sintered as a product. However,
It is not possible to make these conventional torpedoes by injection molding because they prevent the torpedo shape from sticking out of the mold.

An object of the present invention is to provide an injection molding torpedo having a shape capable of molding a carbide alloy by an injection molding method.

[0006]

To achieve the above object, the present invention is directed to a rear surface, a central axis extending in the longitudinal direction, a conical front surface extending to the tip, and a melt extending through the interior from the rear surface inlet to the front surface outlet. A melted material passageway having an inner surface defining a material passage, the molten material passageway having a rear section extending forward from an inlet on the rear surface and a front section extending obliquely outward to connect the rear section to the outlet on the front surface; In the injection molding torpedo having the shortest vertical line extending between the rear inlet and the front outlet, and the shortest vertical line reaching the outlet far from the central axis, the front outlet The front section of the molten material passage extending along the inner surface of the torpedo forming the molten material passage between the inlet and the outlet has a shortest vertical line extending anywhere outside of the central axis along the molten material passage. It is characterized in that retaining a sufficiently tapered inward so as not apart direction.

In addition, the present invention desirably maintains the rear region of the molten material passage slightly tapered inwardly toward the region remote from the inlet of the rear surface.

The invention also desirably provides that both the rear and front sections of the molten material passageway have an annular cross section.

In addition, the invention is preferably such that the shortest vertical line extending along the interior surface forming the molten material passage of the torpedo is substantially straight.

[0010]

1 illustrates a multi-cavity injection molding apparatus having several nozzles 12 in a mold 14 and a distribution manifold 10 connected to each other. Normally, the mold 14 is provided with a large number of plates depending on the application, but in this embodiment, only the cavity plate 16 and the back plate 18 fixed together by bolts 20 are shown for simplification of the drawing. There is.

In the arrangement shown, the distribution manifold 10 is heated by the integral heating wire 22, and the mold 14 is cooled by the cooling water supplied through the cooling passage 24. The distribution manifold 10 includes a central positioning ring 26 and a plurality of insulating elastic spacers 28.
Through the cavity plate 16 and the back plate 18
It is installed between and. An insulating space 30 is maintained between the heated distribution manifold 10 and the cooled mold 14 by an insulating elastic spacer 28.

The rear end portion 32 of each nozzle 12 is fixed to the front surface 36 of the distribution manifold 10 through a bolt 34. Further, the front end portion 38 of each nozzle 12 is provided with a seat portion 40 in which a screw is carved, and the torpedo 42 is fixed by a nozzle seal 44 fitted therein. Each nozzle 12 has an integral heating wire 46 which surrounds and is fitted with a central hole 48. An outer collar 50 is provided at the rear end 32 of each nozzle 12. A flange portion 52 extending forward of the outer collar 50 positions the nozzle 12 and forms an insulating space 56 between the heated nozzle 12 and the cooled mold 14.
It is attached to the seat portion 54 of the airtightly.

A molten material passage 58 extends from the central inlet 60 to the inlet portion 62 of the distribution manifold 10, which melt material passage 58 within the distribution manifold 10 for directing the molten material through the central hole 48 of each nozzle 12. It branches outward. Molten material passes through the molten material passage 64 in the torpedo 42 to a gate 66 through the cavity plate 16 and to a cavity 68 as described in detail below.

With reference to FIGS. 2 and 3, the torpedo 42 has a flat rear surface 70 and a conical front surface 72 extending to a pointed tip 74 coaxial with the central axis 76. The molten material passage 64 extends from the inlet 78 of the rear surface 70 to the front surface 7
A second outlet 80 extends through the torpedo 42.

As shown in FIG. 1, the nozzle seal 44 has a hexagonal engaging portion 82. When the torpedo 42 is fixed at a predetermined position by using this engaging portion 82, it can be firmly tightened by being applied to the rear flange 84. The front end portion 86 of the nozzle seal 44 is the tip 74 of the torpedo 42.
Is accurately fitted to the center of the gate 66, and is fitted with an annular seat portion 88 in the cavity plate 16 surrounding the gate 66. In this arrangement, the molten material flows through the outlet 80 of the molten material passage 64 in the torpedo 42 to the annular space 90 in the mold 14 that surrounds the front surface 72 and further through the gate 66 that surrounds the tip 74 to the cavity 68. The nozzle seal 44 surrounds the annular space 90 and prevents molten material from leaking into the adjacent insulating space 56.

As shown in FIG. 3, the molten material passage 64 through the torpedo 42 has a rear section 92 and an oblique front section 94.
And The rear section 92 is concentric with the central axis 76 of the torpedo 42 and extends forward from the inlet 78 of the rear surface 70. The diagonal front area 94 is the rear area 9
It extends obliquely so as to connect 2 with the outlet 80 facing the front surface 72. The angle by which the front section 94 extends with respect to the central axis 76 is more or less inclined, but is typically about 15 °.

A method of injection molding the shape of the torpedo shown in FIG. 3 in the apparatus shown in FIG. 4 will be described. In the present embodiment, the torpedo is formed of a tungsten carbide-cobalt alloy, but the torpede may be formed using another carbide alloy having corrosion resistance and wear resistance.

As shown in FIG. 4, the torpedo uses molten carbide alloy from the gate 98 to the cavity plate 102.
It is manufactured by injection into the cavity 100 formed between the mold and the ejector side 104 of the mold. A core 107 with a venting insert 105 inserted into the cavity plate 102 and having an ejector sleeve 108 positioned to eject the molded torpedo from the mold.
A cooling pipe 106 extends inside. Although this multi-cavity injection molding apparatus is shown in only a small part, the method of making a torpedo is shown in FIG.
2 is sufficient to describe the shape.

After the cavity 100 is filled, there is an appropriate filling and cooling time, after which the mold is opened along the parting line 110 to project in the direction indicated by arrow 112. After protruding, the torpedo 42 is depolymerized to remove the polymer and then heat-sintered. 16-2 by sintering
The shape shrinks between 0%. After this, it is finished by polishing with a diamond grinding wheel to obtain the final product.

The rear section 92 and the front section 94 of the molten material passage 64 are tapered inwardly toward the front. As shown in FIG. 3, the angled front section 94 defines an inner surface 114 with a shortest vertical line 116 extending between the inlet 78 and the outlet 80. This shortest vertical line 116
Is a point 118 facing the exit 80 far away from the central axis 76.
It is connected to the exit 80 at.

In the present embodiment, the molten material passage 64
The rear section 92 holds a 4 ° taper inside to facilitate ejection by the ejector sleeve 108.
However, the angle by which the front section 94 of the molten material passage 64 extends to project the torpedo 42 in the withdrawal direction shown by arrow 112 in FIG. 4 must be at least sufficiently inclined to maintain a taper inside. In other words, front area 9
4 must be sufficiently tapered inward so that the shortest vertical line 116 extending along the inner surface 114 does not leave outwards anywhere with respect to the centerline 76 along the molten material passage 64.

In particular, in this embodiment, the front section 94 of the molten material passage 64 remains sufficiently tapered inward, yet the shortest vertical line 116 extending along the inner surface 114 of the torpedo 42 is the inlet 78 and the outlet 80. It is straight between. Therefore, as shown in FIG. 4, the torpedo 42 of this shape will tend to exit (arrow 11) even if the front section 94 of the molten material passage 64 is not tapered.
It does not prevent you from sticking out to 2).

In use, the torpedo 42 is assembled in the mold 14 as shown in FIG. 1 and the assembly is completed. A respective heating wire 22, for heating the distribution manifold 10 and the nozzle 12 to a predetermined operating temperature,
Electricity is supplied to 46. Molten material is supplied to the central inlet 60 of the molten material passage 38 from an injection molding machine (not shown) according to a predetermined cycle. The molten material passes through the molten material passage 58 in the distribution manifold 10 to the central hole 48 of each nozzle 12, and further flows into the molten material passage 64 of the torpedo 42, respectively.

The molten material flows from the molten material passage 64 to the annular space 90 in the mold 14 surrounding the front surface 72, and further to the cavity 68 via the gate 66. Here, the nozzle seal 44 prevents the molten material from leaking from the annular space 90 and holds the tip 74 of the torpedo 42 exactly concentric with the gate 66. After the cavity 68 is filled, an appropriate filling time and cooling time are set, the injection pressure is released, the stringing at the gate 66 is avoided, and the molten material supply device is depressurized. After this, the mold 14 is opened to eject the molded product. After the protrusion is completed, the mold 14 is closed. This cycle is continuously repeated with a cycle time determined by the size of the cavity 68 and the type of material to be molded.

[0025]

As described above, according to the present invention, the front region of the molten material passage is arranged so that the shortest vertical line extending along the inner surface of the torpedo does not move outward with respect to the central axis along the molten material passage. I tried to keep the taper inside enough,
Torpedo made of a carbide alloy can be molded by an injection molding method.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of a multi-cavity injection molding apparatus configured by incorporating a torpedo according to the present invention.

FIG. 2 is a perspective view showing the torpedo shown in FIG.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

4 is a sectional view showing a part of a multi-cavity injection molding apparatus used for molding the torpedo shown in FIGS. 1 to 3. FIG.

[Explanation of symbols]

 10 Distribution Manifold 12 Nozzle 42 Torpedo 44 Nozzle Seal 64 Molten Material Passage 68 Cavity 72 Front Surface 92 Rear Area 94 Front Area

Claims (4)

[Claims] 1. A rear surface, a longitudinally extending central axis, a conical front surface extending to a tip, and an inner surface defining a molten material passage extending therethrough from an inlet of the rear surface to an outlet of the front surface. The molten material passageway comprises a rear section extending forward from the inlet of the rear surface and a front section extending obliquely outward to connect the rear section to the outlet of the front surface, the inner surface of the rear surface comprising: An injection molding torpedo having a shortest vertical line extending between an inlet and the outlet of the front surface, the shortest vertical line reaching the outlet far from the central axis, The front section of the molten material passage extending to the outlet on the front surface is the shortest vertical line extending along the inner surface of the torpedo forming the molten material passage between the inlet and the outlet. Torpedo for injection molding, characterized in that retaining a sufficiently tapered inward so as not spaced outward anywhere with respect to the central axis along the melting material path. 2. The injection molding torpedo according to claim 1, wherein the rear region of the molten material passageway retains a slight taper inwardly toward a region of the rear surface away from the inlet. 3. An injection molding torpedo according to claim 2, wherein both said rear and front sections of said melted material passage have an annular cross section. 4. The injection molding torpedo according to claim 3, wherein the shortest vertical line extending along the inner surface forming the molten material passage of the torpedo is substantially straight.